Method for transmitting and receiving d2d signal in wireless communication system, and apparatus therefor

ABSTRACT

The present invention relates to a method and an apparatus for transmitting an acknowledgment/negative-acknowledgement (ACK/NACK) of a terminal in a wireless communication system. More specifically, the method comprises the steps of: receiving a wide area network (WAN)-based downlink signal; and transmitting the ACK/NACK in accordance with first hybrid automatic repeat request (HARQ) processes, based on third wireless resources except for at least one second wireless resource for device-to-device (D2D) among first wireless resources for WAN communication, wherein the HARQ processes are characterized in that WAN uplink transmission timing on the second wireless resource is set up to be shifted to the third wireless resource.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method of transmitting and receiving a D2D(device-to-device) signal in a wireless communication system and anapparatus therefor.

BACKGROUND ART

A 3rd generation partnership project long term evolution (3GPP LTE)(hereinafter, referred to as ‘LTE’) communication system which is anexample of a wireless communication system to which the presentinvention can be applied will be described in brief.

FIG. 1 is a diagram illustrating a network structure of an EvolvedUniversal Mobile Telecommunications System (E-UMTS) which is an exampleof a wireless communication system. The E-UMTS is an evolved version ofthe conventional UMTS, and its basic standardization is in progressunder the 3rd Generation Partnership Project (3GPP). The E-UMTS may bereferred to as a Long Term Evolution (LTE) system. Details of thetechnical specifications of the UMTS and E-UMTS may be understood withreference to Release 7 and Release 8 of “3rd Generation PartnershipProject; Technical Specification Group Radio Access Network”.

Referring to FIG. 1, the E-UMTS includes a User Equipment (UE), basestations (eNode B; eNB), and an Access Gateway (AG) which is located atan end of a network (E-UTRAN) and connected to an external network. Thebase stations may simultaneously transmit multiple data streams for abroadcast service, a multicast service and/or a unicast service.

One or more cells exist for one base station. One cell is set to one ofbandwidths of 1.44, 3, 5, 10, 15 and 20 MHz to provide a downlink oruplink transport service to several user equipments. Different cells maybe set to provide different bandwidths. Also, one base station controlsdata transmission and reception for a plurality of user equipments. Thebase station transmits downlink (DL) scheduling information of downlinkdata to the corresponding user equipment to notify the correspondinguser equipment of time and frequency domains to which data will betransmitted and information related to encoding, data size, and hybridautomatic repeat and request (HARQ). Also, the base station transmitsuplink (UL) scheduling information of uplink data to the correspondinguser equipment to notify the corresponding user equipment of time andfrequency domains that can be used by the corresponding user equipment,and information related to encoding, data size, and HARQ. An interfacefor transmitting user traffic or control traffic may be used between thebase stations. A Core Network (CN) may include the AG and a network nodeor the like for user registration of the user equipment. The AG managesmobility of the user equipment on a Tracking Area (TA) basis, whereinone TA includes a plurality of cells.

Although the wireless communication technology developed based on WCDMAhas been evolved into LTE, request and expectation of users andproviders have continued to increase. Also, since another wirelessaccess technology is being continuously developed, new evolution of thewireless communication technology will be required for competitivenessin the future. In this respect, reduction of cost per bit, increase ofavailable service, use of adaptable frequency band, simple structure andopen type interface, proper power consumption of the user equipment,etc. are required.

In order to assist an eNB and efficiently managing a wirelesscommunication system, a UE periodically and/or aperiodically reportsstate information about a current channel to the eNB. The reportedchannel state information may include results calculated inconsideration of various situations, and accordingly a more efficientreporting method is needed.

DISCLOSURE OF THE INVENTION Technical Task

Based on the aforementioned discussion, the present invention intends toprovide a method of transmitting and receiving a D2D (device-to-device)signal in a wireless communication system and an apparatus therefor.

Technical tasks obtainable from the present invention are non-limitedthe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of transmitting a signal, which istransmitted using an uplink resource of a user equipment in a wirelesscommunication system, includes the steps of receiving a WAN (wide areanetwork) downlink signal and transmitting a response signal using anuplink resource in response to the WAN downlink signal. In this case, ifa WAN signal and a D2D (device-to-device) signal are assigned at thesame time, the uplink resource can be configured to transmit the WANsignal.

Preferably, the response signal may correspond to ACK/NACK(acknowledgement/negative-acknowledgement).

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, amethod of transmitting ACK/NACK(acknowledgement/negative-acknowledgement), which is transmitted by auser equipment in a wireless communication system, includes the steps ofreceiving a downlink signal based on a WAN (wide area network) andtransmitting the ACK/NACK according to first HARQ (hybrid automaticrepeat request) processes based on third radio resources except at leastone second radio resource for D2D (device-to-device) among first radioresources for WAN communication. In this case, the HARQ processes can beconfigured to shift WAN uplink transmission timing on the second radioresource to the third radio resource.

Preferably, the number of the first HARQ processes can be configured tobe greater than the number of second HARQ processes based on the firstradio resources.

Preferably, the downlink signal can include a field redefined toindicate identifier information of the first HARQ processes.

Preferably, the downlink signal is received in a subframe n (where, ncorresponds to a subframe index) and a subframe n+4 can be included inthe third radio resource.

Preferably, the downlink signal is received in a subframe n (where ncorresponds to a subframe index), a subframe n+4 is included in thesecond radio resource, and D2D traffic is not allocated in the subframen+4.

Preferably, the downlink signal may correspond to a downlink datachannel (physical downlink shared channel).

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, a user equipment transmitting a signal using an uplinkresource in a wireless communication system includes a radio frequencyunit and a processor, the processor configured to receive a WAN (widearea network) downlink signal, the processor configured to transmit aresponse signal using an uplink resource in response to the WAN downlinksignal. In this case, if a WAN signal and a D2D (device-to-device)signal are assigned at the same time, the uplink resource can beconfigured to transmit the WAN signal.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a further differentembodiment, a user equipment transmitting ACK/NACK(acknowledgement/negative-acknowledgement) in a wireless communicationsystem includes a radio frequency unit and a processor, the processorconfigured to receive a downlink signal based on a WAN (wide areanetwork), the processor configured to transmit the ACK/NACK according tofirst HARQ (hybrid automatic repeat request) processes based on thirdradio resources except at least one second radio resource for D2D(device-to-device) among first radio resources for WAN communication. Inthis case, the HARQ processes can be configured to shift WAN uplinktransmission timing on the second radio resource to the third radioresource.

Advantageous Effects

According to embodiments of the present invention, it is able toefficiently transmit and receive a D2D (device-to-device) signal in awireless communication system.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a schematic diagram of E-UMTS network structure as one exampleof a wireless communication system;

FIG. 2 is a diagram illustrating structures of a control plane and auser plane of a radio interface protocol between a user equipment andE-UTRAN based on the 3GPP radio access network standard;

FIG. 3 is a diagram illustrating physical channels used in a 3GPP LTEsystem and a general method for transmitting a signal using the physicalchannels;

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system;

FIG. 5 is a diagram for an example of a resource grid for a downlinkslot;

FIG. 6 is a diagram illustrating a structure of a downlink radio frameused in an LTE system;

FIG. 7 is a diagram illustrating a structure of an uplink subframe usedin an LTE system;

FIG. 8 is a diagram for explaining D2D (UE-to-UE) communication;

FIGS. 9 and 10 are diagrams for explaining a result of embodimentsaccording to the present invention;

FIG. 11 is a diagram for a base station and a user equipment applicableto one embodiment of the present invention.

BEST MODE Mode for Invention

The following technology may be used for various wireless accesstechnologies such as CDMA (code division multiple access), FDMA(frequency division multiple access), TDMA (time division multipleaccess), OFDMA (orthogonal frequency division multiple access), andSC-FDMA (single carrier frequency division multiple access). The CDMAmay be implemented by the radio technology such as UTRA (universalterrestrial radio access) or CDMA2000. The TDMA may be implemented bythe radio technology such as global system for mobile communications(GSM)/general packet radio service (GPRS)/enhanced data rates for GSMevolution (EDGE). The OFDMA may be implemented by the radio technologysuch as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, andevolved UTRA (E-UTRA). The UTRA is a part of a universal mobiletelecommunications system (UMTS). A 3rd generation partnership projectlong term evolution (3GPP LTE) is a part of an evolved UMTS (E-UMTS)that uses E-UTRA, and adopts 01-DMA in a downlink and SC-FDMA in anuplink. LTE-advanced (LTE-A) is an evolved version of the 3GPP LTE.

For clarification of the description, although the following embodimentswill be described based on the 3GPP LTE/LTE-A, it is to be understoodthat the technical spirits of the present invention are not limited tothe 3GPP LTE/LTE-A. Also, specific terminologies hereinafter used in theembodiments of the present invention are provided to assistunderstanding of the present invention, and various modifications may bemade in the specific terminologies within the range that they do notdepart from technical spirits of the present invention.

FIG. 2 is a diagram illustrating structures of a control plane and auser plane of a radio interface protocol between a user equipment andE-UTRAN based on the 3GPP radio access network standard. The controlplane means a passageway where control messages are transmitted, whereinthe control messages are used by the user equipment and the network tomanage call. The user plane means a passageway where data generated inan application layer, for example, voice data or Internet packet dataare transmitted.

A physical layer as the first layer provides an information transferservice to an upper layer using a physical channel. The physical layeris connected to a medium access control (MAC) layer via a transportchannel, wherein the medium access control layer is located above thephysical layer. Data are transferred between the medium access controllayer and the physical layer via the transport channel Data aretransferred between one physical layer of a transmitting side and theother physical layer of a receiving side via the physical channel. Thephysical channel uses time and frequency as radio resources. In moredetail, the physical channel is modulated in accordance with anorthogonal frequency division multiple access (OFDMA) scheme in adownlink, and is modulated in accordance with a single carrier frequencydivision multiple access (SC-FDMA) scheme in an uplink.

A medium access control (MAC) layer of the second layer provides aservice to a radio link control (RLC) layer above the MAC layer via alogical channel. The RLC layer of the second layer supports reliabledata transmission. The RLC layer may be implemented as a functionalblock inside the MAC layer. In order to effectively transmit data usingIP packets such as IPv4 or IPv6 within a radio interface having a narrowbandwidth, a packet data convergence protocol (PDCP) layer of the secondlayer performs header compression to reduce the size of unnecessarycontrol information.

A radio resource control (RRC) layer located on the lowest part of thethird layer is defined in the control plane only. The RRC layer isassociated with configuration, re-configuration and release of radiobearers (‘RBs’) to be in charge of controlling the logical, transportand physical channels. In this case, the RB means a service provided bythe second layer for the data transfer between the user equipment andthe network. To this end, the RRC layers of the user equipment and thenetwork exchange RRC message with each other. If the RRC layer of theuser equipment is RRC connected with the RRC layer of the network, theuser equipment is in an RRC connected mode. If not so, the userequipment is in an RRC idle mode. A non-access stratum (NAS) layerlocated above the RRC layer performs functions such as sessionmanagement and mobility management.

One cell constituting a base station eNB is set to one of bandwidths of1.4, 3.5, 5, 10, 15, and 20 MHz and provides a downlink or uplinktransmission service to several user equipments. At this time, differentcells may be set to provide different bandwidths.

As downlink transport channels carrying data from the network to theuser equipment, there are provided a broadcast channel (BCH) carryingsystem information, a paging channel (PCH) carrying paging message, anda downlink shared channel (SCH) carrying user traffic or controlmessages. Traffic or control messages of a downlink multicast orbroadcast service may be transmitted via the downlink SCH or anadditional downlink multicast channel (MCH). Meanwhile, as uplinktransport channels carrying data from the user equipment to the network,there are provided a random access channel (RACH) carrying an initialcontrol message and an uplink shared channel (UL-SCH) carrying usertraffic or control message. As logical channels located above thetransport channels and mapped with the transport channels, there areprovided a broadcast control channel (BCCH), a paging control channel(PCCH), a common control channel (CCCH), a multicast control channel(MCCH), and a multicast traffic channel (MTCH).

FIG. 3 is a diagram illustrating physical channels used in a 3GPP LTEsystem and a general method for transmitting a signal using the physicalchannels.

The user equipment performs initial cell search such as synchronizingwith the base station when it newly enters a cell or the power is turnedon at step S301. To this end, the user equipment synchronizes with thebase station by receiving a primary synchronization channel (P-SCH) anda secondary synchronization channel (S-SCH) from the base station, andacquires information such as cell ID, etc. Afterwards, the userequipment may acquire broadcast information within the cell by receivinga physical broadcast channel (PBCH) from the base station. Meanwhile,the user equipment may identify a downlink channel status by receiving adownlink reference signal (DL RS) at the initial cell search step.

The user equipment which has finished the initial cell search mayacquire more detailed system information by receiving a physicaldownlink shared channel (PDSCH) in accordance with a physical downlinkcontrol channel (PDCCH) and information carried in the PDCCH at stepS302.

Afterwards, the user equipment may perform a random access procedure(RACH) such as steps S303 to S306 to complete access to the basestation. To this end, the user equipment may transmit a preamble througha physical random access channel (PRACH) (S303), and may receive aresponse message to the preamble through the PDCCH and the PDSCHcorresponding to the PDCCH (S304). In case of a contention based RACH,the user equipment may perform a contention resolution procedure such astransmission (S305) of additional physical random access channel andreception (S306) of the physical downlink control channel and thephysical downlink shared channel corresponding to the physical downlinkcontrol channel.

Having performed the above mentioned procedures, the user equipment maybe able to perform a PDCCH/PDSCH reception [S307] and a PUSCH/PUCCH(physical uplink shared channel/physical uplink control channel)transmission [S308] as a general uplink/downlink signal transmissionprocedure. Control information transmitted from the user equipment tothe base station will be commonly referred to as uplink controlinformation (UCI). The UCI includes HARQ ACK/NACK (Hybrid AutomaticRepeat and reQuest Acknowledgement/Negative-ACK), SR (SchedulingRequest), CSI (Channel State Information), etc. In this specification,the HARQ ACK/NACK will be simply referred to as HARQ-ACK or ACK/NACK(A/N). The HARQ-ACK includes at least one of positive ACK (simply,referred to as ACK), negative ACK (NACK), DTX and NACK/DTX. The CSIincludes CQI (Channel Quality Indicator), PMI (Precoding MatrixIndicator), RI (Rank Indication), etc. Although the UCI is generallytransmitted through the PUCCH, it may be transmitted through the PUSCHif control information and traffic data should be transmitted at thesame time. Also, the user equipment may aperiodically transmit the UCIthrough the PUSCH in accordance with request/command of the network.

FIG. 4 is a diagram illustrating a structure of a radio frame used in anLTE system.

Referring to FIG. 4, in a cellular OFDM radio packet communicationsystem, uplink/downlink data packet transmission is performed in a unitof subframe, wherein one subframe is defined by a given time intervalthat includes a plurality of OFDM symbols. The 3GPP LTE standardsupports a type 1 radio frame structure applicable to frequency divisionduplex (FDD) and a type 2 radio frame structure applicable to timedivision duplex (TDD).

FIG. 4(a) is a diagram illustrating a structure of a type 1 radio frame.The downlink radio frame includes 10 subframes, each of which includestwo slots in a time domain. A time required to transmit one subframewill be referred to as a transmission time interval (TTI). For example,one subframe may have a length of 1 ms, and one slot may have a lengthof 0.5 ms. One slot includes a plurality of OFDM symbols in a timedomain and a plurality of resource blocks (RB) in a frequency domain.Since the 3GPP LTE system uses 01-DM in a downlink, OFDM symbolsrepresent one symbol interval. The OFDM symbol may be referred to asSC-FDMA symbol or symbol interval. The resource block (RB) as a resourceallocation unit may include a plurality of continuous subcarriers in oneslot.

The number of OFDM symbols included in one slot may be varied dependingon configuration of a cyclic prefix (CP). Examples of the CP include anextended CP and a normal CP. For example, if the OFDM symbols areconfigured by the normal CP, the number of OFDM symbols included in oneslot may be 7. If the OFDM symbols are configured by the extended CP,since the length of one OFDM symbol is increased, the number of OFDMsymbols included in one slot is smaller than that of OFDM symbols incase of the normal CP. For example, in case of the extended CP, thenumber of OFDM symbols included in one slot may be 6. If a channel stateis unstable like the case where the user equipment moves at high speed,the extended CP may be used to reduce inter-symbol interference.

If the normal CP is used, since one slot includes seven OFDM symbols,one subframe includes 14 OFDM symbols. At this time, first maximum threeOFDM symbols of each subframe may be allocated to a physical downlinkcontrol channel (PDCCH), and the other 01-DM symbols may be allocated toa physical downlink shared channel (PDSCH).

FIG. 4(b) is a diagram illustrating a structure of a type 2 radio frame.The type 2 radio frame includes two half frames, each of which includesfour general subframes, which include two slots, and a special subframewhich includes a downlink pilot time slot (DwPTS), a guard period (GP),and an uplink pilot time slot (UpPTS).

In the special subframe, the DwPTS is used for initial cell search,synchronization or channel estimation at the user equipment. The UpPTSis used for channel estimation at the base station and uplinktransmission synchronization of the user equipment. In other words, theDwPTS is used for downlink transmission, whereas the UpPTS is used foruplink transmission. Especially, the UpPTS is used for PRACH preamble orSRS transmission. Also, the guard period is to remove interferenceoccurring in the uplink due to multipath delay of downlink signalsbetween the uplink and the downlink.

Configuration of the special subframe is defined in the current 3GPPstandard document as illustrated in Table 1 below. Table 1 illustratesthe DwPTS and the UpPTS in case of T_(s)=1/(15000×2048), and the otherregion is configured for the guard period.

TABLE 1 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special subframe Normal cyclic Extended cyclicNormal cyclic Extended cyclic configuration DwPTS prefix in uplinkprefix in uplink DwPTS prefix in uplink prefix in uplink 0  6592 · T_(s)2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 119760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 ·T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 ·T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 ·T_(s) 23040 · T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — —9 13168 · T_(s) — — —

In the meantime, the structure of the type 2 radio frame, that is,uplink/downlink configuration (UL/DL configuration) in the TDD system isas illustrated in Table 2 below.

TABLE 2 Uplink- Downlink- downlink to-Uplink config- Switch-pointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 msD S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D DD D 6 5 ms D S U U U D S U U D

In the above Table 2, D means the downlink subframe, U means the uplinksubframe, and S means the special subframe. Also, Table 2 alsoillustrates a downlink-uplink switching period in the uplink/downlinksubframe configuration of each system.

The structure of the aforementioned radio frame is only exemplary, andvarious modifications may be made in the number of subframes included inthe radio frame, the number of slots included in the subframe, or thenumber of symbols included in the slot.

FIG. 5 is a diagram of a resource grid for a downlink slot.

Referring to FIG. 5, a DL slot includes N_(symb) ^(DL) OFDM symbols intime domain and N_(RB) ^(DL) resource blocks. Since each of the resourceblocks includes N_(sc) ^(RB) subcarriers, the DL slot includes N_(RB)^(DL)×N_(sc) ^(RB) subcarriers in frequency domain FIG. 5 shows oneexample that the DL slot includes 7 OFDM symbols and that the resourceblock includes 12 subcarriers, by which the present invention isnon-limited. For instance, the number of OFDM symbols included in the DLslot can be modified according to a length of a cyclic prefix (CP).

Each element on a resource grid is called Resource Element (RE) and 1single resource element is indicated by a single OFDM symbol index and asingle subcarrier index. A single RB is configured with N_(symb)^(DL)×N_(sc) ^(RB) resource elements. The number N_(RB) ^(DL) ofresource blocks included in the DL slot is dependent on a DLtransmission bandwidth configured in a cell.

FIG. 6 is a diagram illustrating a structure of a downlink subframe.

Referring to FIG. 6, maximum three (four) OFDM symbols located at thefront of the first slot of the subframe correspond to a control regionto which a control channel is allocated. The other OFDM symbolscorrespond to a data region to which a physical downlink shared channel(PDSCH) is allocated. Examples of downlink control channels used in theLTE system include a Physical Control Format Indicator Channel (PCFICH),a Physical Downlink Control Channel (PDCCH), and a Physical Hybrid ARQIndicator Channel (PHICH). The PCFICH is transmitted from the first OFDMsymbol of the subframe, and carries information on the number of OFDMsymbols used for transmission of the control channel within thesubframe. The PHICH carries HARQ ACK/NACK (Hybrid Automatic RepeatreQuest acknowledgement/negative-acknowledgement) signals in response touplink transmission.

The control information transmitted through the PDCCH will be referredto as downlink control information (DCI). The DCI includes resourceallocation information for a user equipment or user equipment group. Forexample, the DCI includes uplink/downlink scheduling information, uplinktransmission (Tx) power control command, etc.

The PDCCH may include transport format and resource allocationinformation of a downlink shared channel (DL-SCH), transport format andresource allocation information of an uplink shared channel (UL-SCH),paging information on a paging channel (PCH), system information on theDL-SCH, resource allocation information of upper layer control messagesuch as random access response transmitted on the PDSCH, a set oftransmission (Tx) power control commands of individual user equipments(UEs) within a random user equipment group, transmission (Tx) powercontrol command, and activity indication information of voice overInternet protocol (VoIP). A plurality of PDCCHs may be transmittedwithin the control region. The user equipment may monitor the pluralityof PDCCHs. The PDCCH is transmitted on aggregation of one or a pluralityof continuous control channel elements (CCEs). The CCE is a logicallocation unit used to provide the PDCCH with a coding rate based onthe status of a radio channel. The CCE corresponds to a plurality ofresource element groups (REGs). The format of the PDCCH and the numberof available bits of the PDCCH are determined depending on the number ofCCEs. The base station determines a PDCCH format depending on the DCIwhich will be transmitted to the user equipment, and attaches cyclicredundancy check (CRC) to the control information. The CRC is maskedwith an identifier (for example, radio network temporary identifier(RNTI)) depending on usage of the PDCCH or owner of the PDCCH. Forexample, if the PDCCH is for a specific user equipment, the CRC may bemasked with cell-RNTI (C-RNTI) of the corresponding user equipment. Ifthe PDCCH is for a paging message, the CRC may be masked with a pagingidentifier (for example, paging-RNTI (P-RNTI)). If the PDCCH is forsystem information (in more detail, system information block (SIB)), theCRC may be masked with system information RNTI (SI-RNTI). If the PDCCHis for a random access response, the CRC may be masked with a randomaccess RNTI (RA-RNTI).

FIG. 7 is a diagram for an example of a structure of an uplink subframein LTE.

Referring to FIG. 7, an uplink subframe includes a plurality of slots(e.g., 2 slots). A slot can include the different number of SC-FDMAsymbols depending on a CP length. An uplink subframe is divided into adata region and a control region in frequency domain. The data regionincludes PUSCH and is used for transmitting a data signal such as audioand the like. The control region includes PUCCH and is used fortransmitting uplink control information (UCI). PUCCH includes an RP pairpositioned at both ends of the data region in frequency axis and hops ata slot boundary.

PUCCH can be used for transmitting control information described in thefollowing.

-   -   SR (scheduling request): Information used for requesting uplink        UL-SCH resource. OOK (on-off keying) scheme is used to transmit        the SR.    -   HARQ ACK/NACK: Response signal for a DL data packet on PDSCH.        This information indicates whether or not a DL data packet is        successfully received. ACK/NACK 1 bit is transmitted in response        to a single DL codeword. ACK/NACK 2 bits are transmitted in        response to two DL codewords.    -   CSI (channel state information): Feedback information on a DL        channel CSI includes a CQI (channel quality indicator) and MIMO        (multiple input multiple output)-related feedback information        includes an RI (rank indicator), a PMI (precoding matrix        indicator), a PTI (precoding type indicator) and the like. 20        bits per subframe are used.

An amount of control information (UCI) capable of being transmitted by auser equipment in a subframe is dependent on the number of SC-FDMAsavailable for transmitting control information. The SC-FDMAs availablefor transmitting the control information correspond to the remainingSC-FDMA symbols except SC-FDMA symbols used for transmitting a referencesignal in a subframe. In case of a subframe to which an SRS (soundingreference signal) is set, a last SC-FDMA symbol of a subframe is alsoexcluded. A reference signal is used for coherent detection of PUCCH.

In the following, D2D (UE-to-UE communication) communication isexplained.

A D2D communication scheme is mainly divided into a scheme of receivinghelp from a network/coordination station (e.g., a base station) and ascheme of not receiving a help from the network/coordination station.

Referring to FIG. 8 (a), a network/coordination station involves intransmitting and receiving a control signal (e.g., a grant message),HARQ, channel state information, etc. and data is transmitted andreceived only between terminals performing D2D communication. And,referring to FIG. 8 (b), while a network provides minimum information(e.g., D2D connection information capable of being used in a cell) only,terminals performing D2D communication form a link to transmit andreceive data.

Based on the aforementioned contents, the present invention proposes amethod of efficiently supporting D2D communication of a D2D UE when D2D(device-to-device) communication is performed by predeterminedresources. In this case, the D2D communication means that a UE directlyperforms communication with a different UE using a radio channel. Inthis case, although the UE corresponds to a terminal of a user, if sucha network device as an eNB transmits and receives a signal according toa communication scheme between UEs, the network device can also beregarded as a sort of UEs.

In the following, for clarity, the present invention is explained basedon a 3GPP LTE system. However, a range of systems to which the presentinvention is applied can be extended to other systems except the 3GPPLTE system. Moreover, embodiments of the present invention can beextensively applied to at least one selected from the group consistingof i) a case that a part of D2D UEs participating in D2D communicationis located at the inside of coverage of a network and the rest of D2DUEs is located at the outside of the coverage of the network (D2Ddiscovery/communication of partial network coverage), ii) a case thatall of the D2D UEs participating in D2D communication are located at theinside of the coverage of the network (D2D discovery/communicationwithin network coverage), and iii) a case that all of the D2D UEsparticipating in D2D communication are located at the outside of thecoverage of the network (D2D discovery/communication outside networkcoverage (for public safety only)).

Moreover, since the D2D communication uses an uplink resourcetransmitted by a UE, the D2D communication transceives interference withWAN (wide area network) communication (i.e., various communications suchas PUCCH or PUSCH transmitted to a base station by a UE). Hence, aresource for the D2D communication can be configured/managed in a mannerof being separated from a resource for the WAN communication in timedomain. However, since the aforementioned operation sets a limit on thetotal amount of resources usable for the WAN communication, it mayreduce performance of the WAN communication. And, in terms of management(e.g., management of WAN DL/UL HARQ timeline) of the WAN communication,a complex scheduling strategy is required in consideration of theresource for the D2D communication.

Hence, various methods for achieving efficient coexistence of the D2Dcommunication and the WAN communication are explained in the embodimentsof the present invention. In the following, for clarity, a D2D UEperforming a D2D communication reception operation and a D2D UEperforming a D2D communication transmission operation are referred to asa “D2D RX UE” and a “D2D TX UE”, respectively.

As an embodiment of the present invention, the D2D RX UE can beconfigured to report identifier (ID) information of D2D TX UEs preferredby the D2D RX UE to a base station to receive D2D signal/data from theD2D TX UEs. Having received the information, the base station canidentify i) a D2D TX UE from which D2D signal/data is received and ii) aD2D communication resource in which D2D communication is mainlyperformed between the D2D RX UE and the D2D TX UE. In particular, theabove-mentioned configuration is more efficient when the base stationknows resources used for an individual D2D TX UE to transmit a D2Dsignal/data.

And, (average) reception power or (average) link quality between the D2DRX UE and the D2D TX UE can be restricted to be i) greater than apredetermined threshold or ii) equal to or greater than thepredetermined threshold. In other word, although a specific D2D RX UE isinterested in a D2D TX UE and intends to receive D2D signal/data fromthe D2D TX UE, if (average) reception power or (average) link qualitybetween the D2D UEs is not greater than the predetermined threshold, theD2D RX UE does not report identifier information of the D2D TX UE to thebase station. In this case, it is able to configure the base station toinform a UE of i) information on the threshold and/or ii) information ona resource used for the D2D RX UE to report identifier information ofthe D2D TX UEs via a predefined signal (e.g., a physical layer signal ora higher layer signal).

As a different embodiment of the present invention, when a groupcast D2Dcommunication is performed, it may be able to configure a D2D RX UE toreport i) identifier information of a group (group ID) to which the D2DRX UE belongs thereto or ii) target identifier (target ID) information.Similarly, having received the information, a base station can identifyi) a D2D TX UE performing groupcast-based D2D signal/data transmissionfrom which D2D signal/data is received and ii) a D2D groupcastcommunication resource in which D2D communication is mainly performedbetween the D2D RX UE and the D2D TX UE.

As a further different embodiment of the present invention, it may beable to configure a D2D RX UE to report information on resources inwhich a D2D communication reception operation is mainly performed by theD2D RX UE to a base station among D2D communication resourcesdefined/allocated/scheduled in advance. In this case, theabove-mentioned reporting operation can be performed based on a periodpredefined or signaled in advance and the information can be implementedby a form such as a bitmap of a predefined length (e.g., a valueidentical to the period). Additionally, it may be able to configure abase station to inform a UE of information on a resource used for theinformation reporting via a predefined signal (e.g., a physical layersignal or a higher layer signal).

For example, if the aforementioned embodiments of the present inventionare applied, the base station is able to identify a location of a D2Dcommunication resource at which a specific D2D RX UE (mainly) performs aD2D communication reception operation. If there exists i) a D2Dcommunication resource not in use or ii) a D2D communication resource ofa low use rate among D2D communication resources allocated/scheduled tothe specific D2D RX UE, the base station is able to reuse the D2Dcommunication resource for the usage of the WAN communication.

Specifically, assume a case that 8 subframes (e.g., D2D SF#A, D2D SF#B,D2D SF#C, D2D SF#D, D2D SF#E, D2D SF#F, D2D SF#G, and D2D SF#H) areallocated/scheduled to a specific D2D RX UE as a D2D communicationresource among 20 subframes. In this case, when the specific D2D RX UEis interested in a D2D TX UE and reports identifier information of theD2D TX UE to a base station to receive D2D signal/data from the D2D TXUE according to the embodiment of the present invention, if it isidentified as 4 subframes (e.g., D2D SF#A, D2D SF#C, D2D SF#E, and D2DSF#G) are (mainly) used for D2D communication between the D2D TX UE andthe D2D RX UE, the base station is able to reuse the remaining 4subframes (i.e., D2D SF#B, D2D SF#D, D2D SF#F, and D2D SF#H) for theusage of the WAN communication. In this case, the remaining 4 subframes(i.e., D2D SF#B, D2D SF#D, D2D SF#F, and D2D SF#H) can be used for i) ausage of (re)transmitting (WAN communication-related) PUSCH or ii) ausage of transmitting information on whether or not previously received(WAN communication-related) PDSCH is successfully received (i.e., ULACK/NACK information), etc.

Specifically, since the base station has identified that the remaining 4subframes are able to be (re)used for the usage of the WAN communicationin the aspect of the specific D2D RX UE, the base station can performPDSCH transmission at previous timings (i.e., D2D SF#(B-4), D2DSF#(D-4), D2D SF#(F-4), and D2D SF#(H-4) (i.e., DL HARQ timeline of FDDsystem is assumed)) in consideration of the 4 subframes. In particular,the specific D2D RX UE is able to transmit UL ACK/NACK information atD2D SF#B, D2D SF#D, D2DSF#F and D2D SF#H in response to PDSCH receivedat D2D SF#(B-4), D2D SF#(D-4), D2D SF#(F-4), and D2D SF#(H-4),respectively.

As a different example, since the base station has identified that theremaining 4 subframes are able to be (re)used for the usage of the WANcommunication in the aspect of the specific D2D RX UE, the base stationcan perform uplink scheduling information (i.e., UL grant information)transmission at previous timings (i.e., D2D SF#(B-4), D2D SF#(D-4), D2DSF#(F-4), and D2D SF#(H-4) (i.e., UL HARQ timeline of FDD system isassumed)) in consideration of the 4 subframes. In particular, thespecific D2D RX UE is able to transmit PUSCH at D2D SF#B, D2D SF#D,D2DSF#F and D2D SF#H based on UL grant information received at D2DSF#(B-4), D2D SF#(D-4), D2D SF#(F-4), and D2D SF#(H-4), respectively.

For example, if D2D communication is configured to be performed using apart of uplink resources in which a UE performs WANcommunication-related transmission, a D2D UE (and/or a non-D2D advancedWAN UE) may have a restriction in transmitting a legacy DL HARQtimeline-based UL ACK/NACK information (in particular, when a WANcommunication resource and a D2D communication resource are separatedfrom each other in time domain).

In this case, the restriction occurred in transmitting the UL ACK/NACKinformation (i.e., UL SF#(N+4)) indicates that a restriction occurs inreceiving PDSCH on WAN communication-related downlink resources (i.e.,DL SF#N) as well. Hence, it may lead to a loss of WAN downlinkcommunication performance.

In order to minimize the loss of the WAN downlink communicationperformance, UL ACK/NACK, which is transmitted in response to PDSCHreceived at a specific timing, can be shifted (to a different timing)based on a predetermined rule/configuration. To this end, it isnecessary to newly configure a DL HARQ RTT (downlink HARQ round triptime) value of a D2D UE (and/or a non-D2D advanced WAN UE) and/or thenumber of DL HARQ processes. For example, it may be able to reconfigurethe DL HARQ RTT value of the D2D UE (and/or the non-D2D advanced WAN UE)and/or the number of DL HARQ processes by 10 and 10, respectively, in aFDD system (i.e., the DL HARQ RTT value and the number of DL HARQprocesses are configured by 8 and 8, respectively, in a legacy FDDsystem).

In this case, if the above-mentioned configuration is applied, it may beable to configure UL ACK/NACK information to be transmitted via aclosest non-D2D UL SF (a resource not used for D2D communication or aresource not configured by a D2D communication resource, hereinafter,SF#K) appearing after an SF including (not including) an SF#(N+4) inresponse to PDSCH received at a specific timing (i.e., DL SF#N). And,retransmission for the PDSCH can be performed in a DL SF#(N+10) inconsideration of the newly defined DL HARQ RTT value (i.e., 10).

If the method of newly configuring the DL HARQ RTT value of the D2D UE(and/or the non-D2D advanced WAN UE) and/or the number of DL HARQprocesses is applied, it is able to redefine a size of a field thatindicates DL HARQ process identifier (ID) information of a DCI formatrelated to downlink scheduling information (i.e., DL grant information)transmission. In this case, the size of the field, which is used forindicating the DL HARQ process identifier (ID) information of the DCIformat related to the DL grant information transmission, may increase to4 bits from 3 bits.

As a further different example, a method of redefining/readjusting afield size can be configured to be restrictively applied to a DCI formatrelated to DL grant information transmitted on USS only. In other word,it may be able to configure a field size (e.g., 3 bits) identical to alegacy field size to be applied to a DCI format related to DL grantinformation transmitted on CSS.

Additionally, it may be able to configure the D2D UE (and/or the non-D2Dadvanced WAN UE) to perform a soft buffer division operation inconsideration of the increased number of DL HARQ processes.

In the following, D2D performance for a plurality of embodimentsproposed by the present invention is explained in detail.

Since priority of WAN is higher than priority of D2D in a subframe inwhich a UE transmits a WAN signal to an eNB, it is unable to transmit aD2D signal in the subframe (at least on an identical subcarrier) and itis unable to receive a D2D signal in the subframe (at least on anidentical subcarrier) due to a half-duplex restriction.

Hence, in case of a FDD system, when a base station schedules uplinktransmission (UL TX) in a subframe n (by transmitting PDSCH, UL grant orPHICH NACK), D2D transmission/reception (D2D TX/RX) is unable to beperformed in a subframe n+4.

The loss of the D2D performance occurs in two directions. If a WAN TX UEcorresponds to a D2D TX UE, all UEs belonging to the coverage of the D2DTX UE are unable to perform a D2D reception operation in a specificsubframe. If a WAN TX UE corresponds to a D2D RX UE, all D2Dtransmission transmitted from D2D TX UEs can be lost in the subframe.

In order to handle the loss of the D2D performance, 4 options can beconsidered in the present invention under an assumption that “N_b, totalnumber of UEs participate in D2D in every cell, 10 randomly selected UEshave WAN traffic for both downlink and uplink according to an FTP2 modelin every cell, and (N_b, total-10) number of UEs do not have WAN trafficin every cell”. In the following, for clarity, it is commonly assumedthat all uplink subframes are semi-statically divided into two subframesets separated from each other, one subframe set is used for WAN andanother subframe set is used for D2D.

Option 1:

When a base station performs WAN scheduling, the base station mayreceive no restriction. In other word, if there exist traffic to betransmitted on downlink (DL)/uplink (UL), the base station can transmitPDSCH or a UL grant in every subframe. In this case, D2D performance canbe considerably reduced.

Option 2:

If a subframe n+4 is included in a D2D subframe set, the base stationmay not transmit PDSCH or a UL grant in a subframe n. In this case, D2Dperformance is not affected. Yet, WAN performance can be reduced due toa scheduling restriction (for protecting D2D TX/RX). If a subframe n+4is included in a WAN subframe set, there is no restriction in performingWAN scheduling in a subframe n.

Option 3:

If a subframe n+4 is included in a D2D subframe set, the base stationcan transmit PDSCH or a UL grant in a subframe n on condition.Specifically, the base station checks whether or not a UE participatesin a D2D operation in the subframe n+4 before PDSCH or a UL grant istransmitted to the UE. If the UE corresponds to a D2D TX UE and there isno D2D traffic to be transmitted in the subframe n+4, the base stationcan transmit the PDSCH or the UL grant only. If the UE corresponds to aD2D RX UE and there is no D2D traffic to be transmitted by all D2D TXUEs within a prescribed range (e.g., a link including RSRP equal to orgreater than −107 dBm) in the subframe n+4, the base station cantransmit the PDSCH or the UL grant only. For example, transmission ofPDSCH (related to a specific D2D RX UE) or a UL grant can be configuredto be determined in consideration of D2D TX UEs interested by thespecific D2D RX UE (or D2D TX UEs intending to perform D2Dcommunication) only (among all D2D TX UEs within the prescribed rangefrom the specific D2D RX UE). In this case, the base station may receiveinformation on the D2D TX UEs interested by the specific D2D RX UE (orthe D2D TX UEs intending to perform D2D communication) (e.g., D2D TX UEID, D2D GROUP ID, i.e., the D2D RX UEs correspond to UEs belonging tothe prescribed range from the specific D2D RX UE) via a predeterminedchannel/signal. Compared to the aforementioned option 2, a WANcommunication-related scheduling restriction can be reduced according toD2D traffic status, thereby increasing WAN performance. If the subframen+4 belongs to the WAN subframe set, there is no restriction inperforming WAN scheduling.

Option 4:

When downlink scheduling is performed, the option 4 is specificallyapplied. In this case, uplink HARQ-ACK timing is shifted to makeHARQ-ACK to be transmitted in a subframe for WAN communication. As aresult, a base station can transmit PDSCH in a random downlink subframeand uplink HARQ-ACK (transmission) corresponding to the PDSCH does notaffect a D2D operation. Due to the HARQ-ACK timing shift, HARQ RTT mayincrease. For clarity, 10 HARQ processes are assumed for the option 4 inthe following.

In the following, results according to the aforementioned 4 options arecompared with each other with reference Tables 3 and 4. First of all,Table 3 shows downlink processing performance in case that there exist 3D2D TX UEs per cell.

TABLE 3 UE Avg. Pkt Y-percentile UE Pkt Thpt [Kbps] X % D2D SFs ScenarioThpt [Kbps] Gain Y = 5 Gain Y = 50 Gain Y = 95 Gain X = 20 Option 110497 N/A 2262 N/A 7642 N/A 31508 N/A Option 2 7605 −28% 1727 −24% 5361−30% 23011 −27% Option 3 7732 −26% 1771 −22% 5498 −28% 21927 −30% Option4 10006  −5% 2205  −3% 7262  −5% 28958  −8% X = 40 Option 1 10497 N/A2262 N/A 7642 N/A 31508 N/A Option 2 5280 −50% 1211 −46% 3690 −52% 15171−52% Option 3 5918 −44% 1377 −39% 4104 −46% 16718 −47% Option 4 10006 −5% 2205  −3% 7262  −5% 28958  −8% X = 60 Option 1 10497 N/A 2262 N/A7642 N/A 31508 N/A Option 2 2904 −72% 802 −65% 1956 −74% 8794 −72%Option 3 4258 −59% 999 −56% 2764 −64% 13003 −59% Option 4 10006  −5%2205  −3% 7262  −5% 28958  −8%

Subsequently, Table 4 shows downlink processing performance in case thatthere exist 6 D2D TX UEs per cell.

TABLE 4 UE Avg. Pkt Y-percentile UE Pkt Thpt [Kbps] X % D2D SFs ScenarioThpt [Kbps] Gain Y = 5 Gain Y = 50 Gain Y = 95 Gain X = 20 Option 110497 N/A 2262 N/A 7642 N/A 31508 N/A Option 2 7605 −28% 1727 −24% 5361−30% 23011 −27% Option 3 7899 −25% 1668 −26% 5580 −27% 22630 −28% Option4 10006  −5% 2205  −3% 7262  −5% 28958  −8% X = 40 Option 1 10497 N/A2262 N/A 7642 N/A 31508 N/A Option 2 5280 −50% 1211 −46% 3690 −52% 15171−52% Option 3 5710 −46% 1267 −44% 3959 −48% 16583 −47% Option 4 10006 −5% 2205  −3% 7262  −5% 28958  −8% X = 60 Option 1 10497 N/A 2262 N/A7642 N/A 31508 N/A Option 2 2904 −72% 802 −65% 1956 −74% 8794 −72%Option 3 3716 −65% 875 −61% 2334 −69% 11285 −64% Option 4 10006  −5%2205  −3% 7262  −5% 28958  −8%

FIG. 9 shows D2D performance in case that there exist 3 D2D TX UEs percell and FIG. 10 shows D2D performance in case that there exist 6 D2D TXUEs per cell. In FIGS. 9 and 10, a vertical axis indicates CDF(cumulative distribution probability) and a horizontal axis indicatesthe number of successful connections.

First of all, as shown in FIGS. 9 and 10, it is able to see that D2Dperformance according to the option 1 is very low. This is because theconsiderable amounts of D2D subframes are lost. On the contrary, it isable to see that WAN performance according to the option 2 isconsiderably reduced. This is because scheduling of an eNB isrestricted. And, compared to the option 2, it is able to see that WANperformance according to the option 3 is increased. In particular, it isable to see that the WAN performance is increasing when more subframesare allocated to D2D to maintain identical D2D performance. However, theWAN performance is still low compared to the option 1. Consequently, itis able to see that the option 4 secures D2D performance of a levelsimilar to a level of the D2D performance of the options 2 and 3 andprovides WAN downlink performance similar to that of the option 1.

Hence, according to the present invention, it may be able to obtainresults described in the following.

-   -   If an eNB performs scheduling, which triggers WAN TX in a        subframe n+4 configured as a D2D subframe, in a subframe n,        since priory of WAN is higher than priority of D2D, D2D        performance is considerably degraded.    -   When a subframe n+4 is configured as a D2D subframe, if an eNB        evades transmitting PDSCH in a subframe n, WAN downlink        performance is considerably degraded due to the loss of downlink        subframes.    -   If HARQ-ACK timing is shifted to make uplink HARQ-ACK to be        transmitted in a subframe which is not configured as a D2D        subframe, it is able to secure both WAN downlink performance and        D2D performance.

Moreover, since the embodiments of the present invention correspond toone of implementation methods of the present invention, it is apparentthat the embodiments of the present invention are considered as a sortof proposed schemes. Although the aforementioned proposed schemes can beindependently implemented, and the aforementioned proposed schemes canalso be implemented in a combination (aggregation) form of a part of theproposed schemes.

FIG. 11 is a diagram for a base station and a user equipment applicableto one embodiment of the present invention.

If a relay is included in a wireless communication system, communicationis performed between a base station and the relay in backhaul link andcommunication is performed between the relay and a user equipment inaccess link. Hence, the base station and the user equipment shown in thedrawing can be replaced with the relay in accordance with a situation.

Referring to FIG. 11, a wireless communication system includes a basestation (BS) 110 and a user equipment (UE) 120. The BS 110 includes aprocessor 112, a memory 114 and a radio frequency (RF) unit 116. Theprocessor 112 can be configured to implement the proposed functions,processes and/or methods. The memory 114 is connected with the processor112 and then stores various kinds of information associated with anoperation of the processor 112. The RF unit 116 is connected with theprocessor 112 and transmits and/or receives a radio signal. The userequipment 120 includes a processor 122, a memory 124 and a radiofrequency (RF) unit 126. The processor 122 can be configured toimplement the proposed functions, processes and/or methods. The memory124 is connected with the processor 122 and then stores various kinds ofinformation associated with an operation of the processor 122. The RFunit 126 is connected with the processor 122 and transmits and/orreceives a radio signal. The base station 110 and/or the user equipment120 may have a single antenna or multiple antennas.

The above-described embodiments correspond to combinations of elementsand features of the present invention in prescribed forms. And, therespective elements or features may be considered as selective unlessthey are explicitly mentioned. Each of the elements or features can beimplemented in a form failing to be combined with other elements orfeatures. Moreover, it is able to implement an embodiment of the presentinvention by combining elements and/or features together in part. Asequence of operations explained for each embodiment of the presentinvention can be modified. Some configurations or features of oneembodiment can be included in another embodiment or can be substitutedfor corresponding configurations or features of another embodiment. And,it is apparently understandable that an embodiment is configured bycombining claims failing to have relation of explicit citation in theappended claims together or can be included as new claims by amendmentafter filing an application.

In this disclosure, a specific operation explained as performed by abase station may be performed by an upper node of the base station insome cases. In particular, in a network constructed with a plurality ofnetwork nodes including a base station, it is apparent that variousoperations performed for communication with a user equipment can beperformed by a base station or other networks except the base station.‘Base station (BS)’ may be substituted with such a terminology as afixed station, a Node B, an eNode B (eNB), an access point (AP) and thelike.

Embodiments of the present invention can be implemented using variousmeans. For instance, embodiments of the present invention can beimplemented using hardware, firmware, software and/or any combinationsthereof. In the implementation by hardware, a method according to eachembodiment of the present invention can be implemented by at least oneselected from the group consisting of ASICs (application specificintegrated circuits), DSPs (digital signal processors), DSPDs (digitalsignal processing devices), PLDs (programmable logic devices), FPGAs(field programmable gate arrays), processor, controller,microcontroller, microprocessor and the like.

In case of the implementation by firmware or software, a methodaccording to each embodiment of the present invention can be implementedby modules, procedures, and/or functions for performing theabove-explained functions or operations. Software code is stored in amemory unit and is then drivable by a processor.

The memory unit is provided within or outside the processor to exchangedata with the processor through the various means known in public.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention that come within thescope of the appended claims and their equivalents.

INDUSTRIAL APPLICABILITY

Although the method of transmitting and receiving a D2D(device-to-device) signal in a wireless communication system and anapparatus therefor are described centering on examples applied to 3GPPLTE system, it may be applicable to various wireless communicationsystems as well as to the 3GPP LTE system.

What is claimed is:
 1. A method of transmitting control information by adevice in a wireless communication system, the method comprising:receiving a downlink signal from a base station in a first time unit;when a second time unit is a time unit for a device-to-device (D2D)communication, shifting a transmission time of anacknowledgement/negative-acknowledgement (ACK/NACK) signal about thedownlink signal to transmit the ACK/NACK signal in a time unit for anon-D2D communication after the second time unit; and when the secondtime unit is a time unit for the non-D2D communication, transmitting theACK/NACK signal in the second time unit, wherein an index of the firsttime unit is a positive integer n, and an index of the second time unitis (n+k), wherein k denotes a predetermined positive integer indicatingan ACK/NACK transmission timing.
 2. The method of claim 1, wherein thedownlink signal is received via a physical downlink shared channel. 3.The method of claim 1, wherein if the second time unit is the time unitfor the D2D communication, the transmission time of the ACK/NACK signalis shifted by shifting a hybrid automatic repeat request (HARQ) processfor the downlink signal.
 4. The method of claim 1, wherein k is equal to4.
 5. The method of claim 1, wherein a time unit includes at least oneof subframe, slot or resource block.
 6. A device for transmittingcontrol information in a wireless communication system, the devicecomprising: a transceiver to transmit/receive a signal; and a processoroperably coupled with the transceiver and configured to: receive, viathe transceiver, a downlink signal from a base station in a first timeunit; when a second time unit is a time unit for a device-to-device(D2D) communication, shift a transmission time of anacknowledgement/negative-acknowledgement (ACK/NACK) signal about thedownlink signal to transmit the ACK/NACK signal in a time unit for anon-D2D communication after the second time unit; and when the secondtime unit is a time unit for the non-D2D communication, transmit, viathe transceiver, the ACK/NACK signal in the second time unit, wherein anindex of the first time unit is a positive integer n, and an index ofthe second time unit is (n+k), wherein k denotes a predeterminedpositive integer indicating an ACK/NACK transmission timing.
 7. Thedevice of claim 6, wherein the downlink signal is received via aphysical downlink shared channel.
 8. The device of claim 6, wherein ifthe second time unit is the time unit for the D2D communication, thetransmission time of the ACK/NACK signal is shifted by shifting a hybridautomatic repeat request (HARQ) process for the downlink signal.
 9. Thedevice of claim 6, wherein k is equal to
 4. 10. The device of claim 6,wherein a time unit includes at least one of subframe, slot or resourceblock.